Adjusting Clutch Slip Based on Sensed Parameter of Transmission Shaft to Control Vehicle NVH

ABSTRACT

A vehicle powertrain includes a transmission and a clutch. The slip of the clutch is adjusted to a predefined target where a sensed parameter of a shaft of the transmission corresponds to a specified noise, vibration, and harshness (NVH) level in the powertrain. The sensed parameter of the transmission shaft may be one of acceleration, speed, and torque of the transmission shaft. The transmission shaft may be one of the input shaft and output shaft of the transmission.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.13/685,793, filed Nov. 27, 2012, the disclosure of which is herebyincorporated in its entirety by reference herein.

TECHNICAL FIELD

The present invention relates to adjusting slip of a clutch upstream ofa transmission in order to control noise, vibration, and harshness (NVH)effects in the vehicle powertrain.

BACKGROUND

Vehicle powertrains include an engine and a transmission, wherein torque(or power) produced by the engine is transferred to the drive wheelsthrough the transmission. In some powertrains, the engine is connectedto the transmission via a clutch such as a bypass clutch on a torqueconverter equipped transmission or an input clutch on a dual clutch orautomated manual transmission. Herein, the bypass clutch on a torqueconverter will be used to refer to either clutch type.

The slip of the bypass clutch is indicative of the amount of engagementof the torque converter. Operation of the bypass clutch at a high slipprovides a large hydrodynamic coupling between the engine and thetransmission which dampens driveline disturbances caused by torquedisturbances from the engine, but reduces energy efficiency of thevehicle. Operation of the bypass clutch at a low slip provides a smallhydrodynamic coupling between the engine and the transmission which doesnot attenuate the driveline disturbances, but provides improved energyefficiency of the vehicle. As described, the clutch slip allows for areduction in the amount of engine torsional disturbance that reaches thetransmission input and ultimately the vehicle occupants. The drivelinedisturbances are a measure of noise, vibration, and harshness (NVH)effects in the vehicle powertrain. Thus, while a large clutch slipreduces the NVH effects, it increases fuel consumption.

An off-line process which includes evaluation by vehicle NVH experts hasbeen used to determine a desired amount of clutch slip (corresponding toa tolerable amount of NVH) for a given vehicle operating state. Thisprocess develops tables of allowable clutch slip versus various vehicleoperating states such as engine speed, engine torque, gear selected, andtemperature. This procedure is based on audible and tactile inputs tothe driver.

Other NVH methods use measured acceleration of the transmission inputshaft. The input shaft acceleration is felt to be the controlling factorof NVH level by some in the NVH community and is used as thequantitative underpinning of a qualitative process. Tables are built torelate acceptable NVH level to transmission input shaft acceleration,and transmission input shaft acceleration versus clutch slip.

The tables developed from the noted processes do not take into accountall possible contributors to the excitation, nor do they take intoaccount vehicle aging. As such, the tables may be inaccurate leadingeither to unacceptable NVH level or excessive fuel consumption.

SUMMARY

In one embodiment, a method for a powertrain having a transmission and aclutch is provided. The method includes adjusting slip of the clutch toa predefined target in which torque of a shaft of the transmissioncorresponds to a specified level of noise, vibration, and harshness(NVH) in the powertrain.

The shaft may be an input shaft or an output shaft of the transmission.

The method may further include sensing the torque of the shaft using asensor in communication with the shaft and detecting an amount of NVH inthe powertrain based on the torque of the shaft. The slip of the clutchmay be adjusted to the target such that the amount of NVH in thepowertrain based on the torque of the shaft corresponds to the specifiedlevel of NVH. The amount of NVH may be detected based on a magnitude ofthe torque of the shaft, wherein the magnitude of the torque is one ofpeak-to-peak change, half peak-to-peak change, and root-mean-square ofthe torque of the shaft.

In one embodiment, another method for a powertrain having a transmissionand a clutch is provided. This method includes detecting an amount ofNVH in the powertrain based on torque of a shaft of the transmission andadjusting slip of the clutch to a predefined target corresponding to aspecified level of NVH upon the amount of NVH exceeding the specifiedlevel. The shaft may be an input shaft or an output shaft of thetransmission.

This method may further include sensing the torque of the shaft using asensor in communication with the shaft to detect the amount of NVH basedon the torque of the shaft.

In one embodiment, another method for a powertrain having a transmissionand a clutch is provided. This method includes adjusting slip of theclutch to a predefined target in which a sensed parameter of an outputshaft of the transmission corresponds to a specified level of NVH in thepowertrain. The sensed parameter of the output shaft may be torque,speed, or acceleration of the output shaft.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a block diagram of an exemplary vehicle powertrain inaccordance with an embodiment of the present invention;

FIG. 2 illustrates a flowchart describing the general operation of acontrol strategy in accordance with an embodiment of the presentinvention for adjusting slip of a clutch of a vehicle powertrain to atarget where a magnitude of a sensed parameter of a shaft of atransmission of the vehicle powertrain corresponds to a desired NVHlevel in a vehicle powertrain;

FIG. 3 illustrates a flowchart describing operation of the controlstrategy in generating information regarding the magnitude of the sensedparameter of the transmission shaft;

FIG. 4 illustrates a flowchart describing operation of the controlstrategy in identifying a static clutch slip request;

FIG. 5 illustrates a flowchart describing operation of the controlstrategy in identifying a transient clutch slip request;

FIG. 5A illustrates a flowchart describing operation of the controlstrategy in arbitrating between the static slip request and thetransient slip request; and

FIG. 6 illustrates a flowchart describing operation of the controlstrategy in an off-line identification process for building base tables.

DETAILED DESCRIPTION

Detailed embodiments of the present invention are disclosed herein;however, it is to be understood that the disclosed embodiments aremerely exemplary of the invention that may be embodied in various andalternative forms. The figures are not necessarily to scale; somefeatures may be exaggerated or minimized to show details of particularcomponents. Therefore, specific structural and functional detailsdisclosed herein are not to be interpreted as limiting, but merely as arepresentative basis for teaching one skilled in the art to variouslyemploy the present invention.

Referring now to FIG. 1, a block diagram of an exemplary powertrainsystem 10 for a vehicle in accordance with an embodiment of the presentinvention is shown. Powertrain system 10 includes an engine 12, a torqueconverter 14, and a multiple-ratio automatic transmission 16. Outputshaft 18 of engine 12 is connected to the upstream side of torqueconverter 14. The upstream side of transmission 16 is connected to thedownstream side of torque converter 14 and the downstream side oftransmission 16 is connected to drive wheels 20 of the vehicle. Thedriving force applied from engine 12 is transmitted through torqueconverter 14 and transmission 16 to drive wheels 20 thereby propellingthe vehicle.

Torque converter 14 includes an impeller rotor fixed to output shaft 18of engine 12 and a turbine rotor fixed to input shaft 22 of transmission16. The turbine of torque converter 14 can be driven hydro-dynamicallyby the impeller of torque converter 14. Thus, torque converter 14 mayprovide a hydraulic coupling between engine output shaft 18 andtransmission input shaft 22.

Torque converter 14 further includes a torque converter clutch 24 (i.e.,bypass clutch 24). Bypass clutch 24 is controllable between an engagedposition (i.e., a locked-up position, an applied position, etc.) and adisengaged position (i.e. an unlocked position, etc.). In the engagedposition, bypass clutch 24 frictionally couples the impeller and theturbine of torque converter 14, which eliminates the hydraulic couplingbetween these components. In the disengaged position, bypass clutch 24permits the hydraulic coupling between these components.

When bypass clutch 24 is disengaged, the hydraulic coupling of torqueconverter 14 absorbs and attenuates vibrations and disturbances in thepowertrain. The source of such disturbances includes the engine torquefrom engine 12 for propelling the vehicle. Fuel economy of the vehicleis reduced when bypass clutch 24 is disengaged due to the lossesassociated with the hydraulic coupling.

Bypass clutch 24 may be controlled through operation of a clutch valve26. In response to a control signal, clutch valve 26 pressurizes andvents bypass clutch 24 to engage and disengage the frictional couplingbetween the impeller and turbine. The apply pressure of bypass clutch 24can be controlled so that bypass clutch 24 is neither fully engaged norfully disengaged and instead is modulated to produce a variablemagnitude of slip between the impeller and turbine in torque converter14. The slip of torque converter 14 (i.e., the slip of bypass clutch 24,the clutch slip) corresponds to the difference in the speeds of theimpeller and the turbine of torque converter 14. The clutch slipdecreases as bypass clutch 24 approaches the engaged position andincreases as bypass clutch 24 approaches the disengaged position.

Engine 12 is an internal combustion engine such as a gasoline, diesel,or natural gas powered engine and is a primary source of power forpowertrain system 10. Engine 12 generates an engine power andcorresponding engine torque is supplied via engine output shaft 18. Theengine power corresponds to the product of engine torque and the enginespeed. At least a portion of the engine torque passes from engine 12through torque converter 14 to transmission 16 in order to drive thevehicle with engine 12.

Transmission 16 includes multiple discrete gear ratios. Transmission 16includes an output shaft 28 that is connected to a differential 30.Drive wheels 20 are connected to differential 30 through respectiveaxles. With this arrangement, transmission 16 transmits a powertrainoutput torque to drive wheels 20.

Transmission 16 includes planetary gear sets (not shown) that areselectively placed in different gear ratios by selective engagement offriction elements (not shown) to establish the desired multiple discretedrive ratios. The friction elements are controllable through a shiftschedule that connects and disconnects elements of the planetary gearsets to control the ratio between the transmission output and thetransmission input. Transmission 16 is automatically shifted from oneratio to another based on the needs of the vehicle and provides apowertrain output torque to transmission output shaft 28 whichultimately drives drive wheels 20. The kinetic details of transmission16 can be implemented by a wide range of transmission arrangements.Transmission 16 is an example of a transmission arrangement for use withembodiments of the present invention. Any multiple ratio transmissionthat accepts an input torque and then provides torque to an output shaftat the different ratios is acceptable for use with embodiments of thepresent invention.

Powertrain system 10 further includes a powertrain controller 32 whichconstitutes a vehicle system controller. Controller 32 is configured tocontrol the operation of engine 12. Controller 32 is further configuredto control the operation of bypass clutch 24 via clutch valve 26. Again,the slip of torque converter 14 (i.e., the slip of bypass clutch 24, theclutch slip) corresponds to the difference between the input and outputrotational speeds of torque converter 14. The output rotational speedapproaches the input rotational speed as bypass clutch 24 approaches theengaged position such that the clutch slip decreases. Conversely, theoutput rotational speed diverges from the input rotational speed asbypass clutch 24 approaches the disengaged position such that the clutchincreases. The clutch slip may be measured or estimated using one ormore corresponding sensors and operating parameters. For example,powertrain system 10 further includes a slip sensor 33 configured tosense the clutch slip and provide information indicative of the clutchslip to controller 32.

Powertrain system 10 further includes a transmission input shaft sensor34 (“input sensor 34”) and a transmission output shaft sensor 36(“output sensor 36”). Input sensor 34 is associated with input shaft 22of transmission 16 and is configured to sense the torque and/or speed oftransmission input shaft 22. Output sensor 36 is associated with outputshaft 28 of transmission 16 and is configured to sense the torque and/orspeed of transmission output shaft 28.

Either sensor 34, 36 may be a strain-gauge base system, aforce-resistive elastomer sensor, a piezoelectric load cell, or amagneto-elastic torque sensor. In one embodiment, each sensor 34, 36 isa magneto-elastic torque sensor as described in U.S. Pat. Nos.6,145,387; 6,047,605; 6,553,847; and 6,490,934. Such magneto-elastictorque sensors enable accurate measurements of torque exerted onto arotating shaft without requiring a physical contact between a magneticflux sensing element and the shaft. Each torque sensor 34, 36 mayinclude a counterpart sensor for sensing speed and/or acceleration ofthe respective shafts or may be further configured for sensing bythemselves the speed and/or the acceleration of the respective shafts.

As described, sensors 34, 36 are in communication with transmissioninput shaft 22 and transmission output shaft 28, respectively, and areconfigured to sense the torque and/or speed and/or acceleration of thecorresponding shafts. Sensors 34, 36 respectively provide sensor signalsindicative of the torque and/or speed and/or acceleration of thecorresponding shafts to controller 32.

According to a control strategy in accordance with embodiments of thepresent invention, controller 32 uses the sensor signals from at leastone of sensors 34, 36 to control the clutch slip (i.e., bypass clutch24) in order to reduce the noise, vibration, and harshness (NVH) effectsin powertrain system 10. The controller adjusts the slip of clutch 24 toa target where a magnitude of a sensed parameter of a shaft oftransmission 26 corresponds to a desired NVH level in powertrain system10. The shaft of transmission 26 may be either transmission input shaft22 or transmission output shaft 28. The sensed parameter of transmissionshaft 22, 28 may be one of torque, speed, and acceleration oftransmission shaft 22, 28. The magnitude of the sensed parameter oftransmission shaft 22, 28 may be, for example, one of the peak-to-peakchange, half peak-to-peak change, and root-mean-square (RMS) value ofthe sensed parameter of transmission shaft 22, 28.

For example, the control strategy controls the clutch slip based on themagnitude of the peak-to-peak change (i.e., “fluctuation” as usedherein), half peak-to-peak change, and RMS value of at least one of: (i)the torque of transmission input shaft 22, (ii) the speed oftransmission input shaft 22, (iii) the acceleration of transmissioninput shaft 22; (iv) the torque of transmission output shaft 28, (v) thespeed of transmission output shaft 28, and/or (vi) the acceleration oftransmission output shaft 28 in order to reduce the NVH effects.Collectively, items (i) through (vi) are referred to as transmissioninput/output shaft torque/speed/acceleration peak-to-peak change/halfpeak-to-peak change/RMS value.

The item (i) of the magnitude of the peak-to-peak change of the torqueof transmission input shaft 22 will be used herein when referring to anyof items (i) through (vi) individually. In item (i), the transmissionshaft is transmission input shaft 22, the sensed parameter is the torqueof transmission input shaft 22, and the magnitude of the sensedparameter of transmission input shaft 22 is the peak-to-peak change ofthe torque of the transmission input shaft 22.

The peak-to-peak change of a variable is the difference in magnitudebetween the maximum positive and the maximum negative amplitudes of thevariable. As such, the peak-to-peak change of a variable is thedifference between the maximum and minimum amplitudes of the variable.For example, the peak-to-peak change of the torque of transmission inputshaft 22 is the difference in magnitude between the maximum amplitude ofthe torque of transmission input shaft 22 and the minimum amplitude ofthe torque of transmission input shaft 22. Likewise, the halfpeak-to-peak change of a variable and the RMS value of a variable areused herein in accordance with their ordinary meanings.

The control strategy provides a closed-loop control of the clutch slip(e.g., a closed-loop control of bypass clutch 24) to reduce NVH effectssuch as those produced by firing pulses of engine 12. The magnitude ofthe sensed parameter of the transmission shaft corresponds to the NVHlevel present in a vehicle powertrain such as powertrain system 10.Thus, for instance, the peak-to-peak change in the torque oftransmission input shaft 22 is a surrogate for the NVH level present inpowertrain system 10. The control strategy is based on, in real time,reading torque changes or fluctuations of transmission input shaft 22using input sensor 34 in order to learn of the amount of NVH present andadjusting bypass clutch 24 to have a desired level of clutch slip whichwill provide a tolerable amount of NVH.

The control strategy ensures uniform engine excited NVH based on arobust method to measure and adjust measured engine excitation byclosed-loop control of the clutch slip. As described herein, the methodmay further feed forward clutch slip based on anticipated changes invehicle operating conditions and adapt clutch slip tables based onmeasured engine excitation.

Again, in one embodiment, the control strategy uses input sensor 34 tomeasure the magnitude of the peak-to-peak change in the torque oftransmission input shaft 22. The magnitude of the peak-to-peak change inthe torque of transmission input shaft 22 corresponds to the level ofNVH present in powertrain system 10. Similarly, in another embodiment,the control strategy uses input sensor 34 to measure the magnitude ofthe peak-to-peak change in the speed (or acceleration) of transmissioninput shaft 22. The magnitude of the peak-to-peak change in the speed(or acceleration) of transmission input shaft 22 corresponds to thelevel of NVH present in powertrain system 10. Likewise, in otherembodiments, the control strategy uses output sensor 36 to measure themagnitude of the peak-to-peak change in the torque and/or speed and/oracceleration of transmission output shaft 28. The magnitude of thepeak-to-peak change in the torque, speed, and acceleration oftransmission output shaft 22 each corresponds to the level of NVHpresent in powertrain system 10.

As indicated above, using input sensor 34 to measure the magnitude ofthe peak-to-peak change in the torque of transmission input shaft 22 inorder to learn of the NVH level present in powertrain system 10 is usedherein as the example. The control strategy uses the torque measurementof transmission input shaft 22 to correlate between vehicle NVH ratingsand the peak-to-peak change in the torque of transmission input shaft 22under multiple vehicle operating conditions.

In general, the control strategy includes: calculating an acceptableamount of transmission input shaft torque peak-to-peak measurement basedon NVH rating required or requested; instantaneously adjusting a clutchslip target to meet the desired peak-to-peak torque level; and measuringactual peak-to-peak torque at a measured slip and adjusting the amountof clutch slip to reduce peak-to-peak torque (and thereby NVH level) toan acceptable level. As such, the latter step provides a closed-loopcontrol on peak-to-peak torque (i.e., NVH).

Other aspects of the control strategy may include the following. Acalibration process is outlined for gathering data for base calibrationtables. A multi-dimensional table of clutch slip versus peak-to-peaktorque table is updated as a function of vehicle operating conditions.Minimum and maximum clutch slip levels can be considered to prevent overadjustment. Feed forward features are provided to predict requiredclutch slip level based on vehicle operating conditions and inputs suchas accelerator pedal and engine speed using the learned tables.Conditions where sensor acceleration is not due to engine firingfrequency are identified and the response to those conditions isappropriately limited. For example, a filter to match multiples ofengine speed (orders) to filter out road inputs can be employed.

Referring now to FIG. 2, with continual reference to FIG. 1, a flowchart50 describing the general operation of a control strategy in accordancewith an embodiment of the present invention for adjusting the clutchslip (e.g., for adjusting the slip of bypass clutch 24) to a targetwhere a magnitude (peak-to-peak change, half peak-to-peak change, RMSvalue, etc.) of a sensed parameter (torque, speed, acceleration) of ashaft of transmission 16 (transmission input shaft 22, transmissionoutput shaft 28) corresponds to a desired NVH level to thereby controlNVH effects in a vehicle powertrain is shown. Again, the magnitude ofthe transmission input shaft torque peak-to-peak change will be used asthe representative example.

The general operation of the control strategy includes obtaining arequired or requested NVH rating for a given vehicle operating conditionas shown in block 52. An acceptable amount of a magnitude of a parameterof the shaft (e.g., the shaft torque peak-to-peak change) based on therequested NVH rating is identified to controller 32 as shown in block54. Controller 32 adjusts a target of the clutch slip to a value formeeting the acceptable amount of the magnitude of the parameter of theshaft (e.g., the shaft torque peak-to-peak change) as shown in block 56.Input sensor 34 senses the actual amount of the magnitude of theparameter of the shaft (e.g., the shaft torque peak-to-peak change) andprovides information indicative of same to controller 32 as shown inblock 58. Slip sensor 33 senses the actual amount of clutch slip andprovides information indicative of same to controller as shown in block60. Controller 32 adjusts the clutch slip to the target in order reducethe actual amount of the magnitude of the parameter of the shaft (e.g.,the shaft torque peak-to-peak change), and thereby the NVH levelpresent, to the acceptable amount, and thereby to the requested NVHrating, as shown in block 62. The clutch slip and the magnitude of theparameter for the vehicle operating condition are then stored as shownin block 63.

Referring now to FIG. 3, with continual reference to FIGS. 1 and 2, aflowchart 70 describing operation of the control strategy in generatinginformation regarding the magnitude of the sensed parameter of thetransmission shaft is shown. Again, the magnitude of the transmissioninput shaft torque peak-to-peak change will be used as therepresentative example.

This operation includes controller 32 obtaining from input sensor 34 thesensed transmission shaft parameter (e.g., shaft torque) as shown inblock 72. Controller 32 obtains from slip sensor 33 the sensed clutchslip as shown in block 74. Controller 32 further obtains informationindicative of the current operating conditions including turbine speed,engine speed, engine torque, temperature, and gear state as shown inblock 76.

Controller 32 uses the sensed parameter to generate the magnitude of thesensed parameter as shown in block 78. For instance, controller uses thesensed torque to generate the torque peak-to-peak change in block 78.Controller 32 identifies the magnitude of the sensed parameter at thecurrent operating conditions along with the measured clutch slip asshown in block 80. For instance, controller 32 identifies the shafttorque peak-to-peak change at the current operating conditions alongwith the measured clutch slip in block 80. Controller 32 updates a tableof magnitude of the sensed parameter versus vehicle operating conditionswith the information identified by controller 32 in block 80 as shown inblock 82. For instance, in block 82, controller 32 updates a table oftorque peak-to-peak change versus vehicle operating conditions with theinformation identified by controller 32 in block 80. The table of torquepeak-to-peak change versus vehicle operating conditions ismultidimensional as the shaft torque peak-to-peak is a function ofclutch slip and various operating conditions. The various operatingconditions include gear mode; engine torque; engine, transmission, orother temperature that is measurable and affects NVH level; and enginespeed and vehicle speed.

Controller 32 employs the following operations in generating informationregarding the magnitude of the shaft torque peak-to-peak change.Controller 32 recalls the time of the last peak and detects the currentpeak from the shaft torque signal from input sensor 34. Controller 32calculates a moving average of the shaft torque peak-to-peak and amoving average of the actual shaft torque. Controller 32 calculates amoving average of the clutch slip and the other operating conditions.Controller 32 then updates the table of torque peak-to-peak changeversus operating conditions.

Referring now to FIG. 4, with continual reference to FIGS. 1, 2, and 3,a flowchart 90 describing operation of the control strategy inidentifying a static clutch slip request is shown. Again, the magnitudeof the transmission input shaft torque peak-to-peak change will be usedas the representative example. Controller 32 identifies a static clutchslip request at block 92 based on various inputs. As shown in FIG. 4,the various inputs include: the magnitude of the sensed parameter (e.g.,the shaft torque peak-to-peak change) at the current operatingconditions including the measured clutch slip of block 80; an upperlimit of allowed clutch slip as shown in block 94; a lower limit ofallowed clutch slip as shown in block 96; a base table of requiredclutch slip versus operating conditions as shown in block 98; and theNVH level versus the magnitude of the sensed parameter (e.g., the torquepeak-to-peak change) (again, the torque peak-to-peak change is asurrogate for the NVH level) as shown in block 100. Controller 32commands the static clutch slip request to clutch valve 26 in order tocontrol the clutch slip accordingly as shown in block 102.

The base table of required clutch slip versus operating conditionscontains a base level of clutch slip to meet NVH requirements for baseor starting condition. This information is updated over time ascontroller 32 updates the table of the magnitude of the sensed parameter(e.g., torque peak-to-peak change) versus operating conditions in block82 per the processing shown in FIG. 3.

Controller 32 employs the following operations in identifying the staticclutch slip request. Controller 32 calculates a NVH level based on themagnitude of the sensed parameter (e.g., shaft torque peak-to-peakchange) at the current operating conditions. Controller 32 uses thelearned magnitude of the sensed parameter (e.g., shaft torquepeak-to-peak) versus clutch slip and operating conditions to calculateclutch slip required at the magnitude of the sensed parameter (e.g.,shaft torque peak-to-peak change). Controller 32 checks if the clutchslip at the operating conditions is out of bounds low or out of boundshigh based on the lower and upper limits on clutch slip allowed.Controller 32 clips the commanded static clutch slip request based onthese limits. Controller 32 adjusts the commanded clutch slip to matchclutch slip required if not using transient adjustment (which isdescribed with reference to FIG. 5).

Referring now to FIG. 5, with continual reference to FIGS. 1, 2, 3, and4, a flowchart 110 describing operation of the control strategy inidentifying a transient clutch slip request is shown. Again, themagnitude of the transmission input shaft torque peak-to-peak changewill be used as the representative example. Controller 32 identifies atransient clutch slip request at block 112 based on various inputs. Asshown in FIG. 5, the various inputs include: the magnitude of the sensedparameter (e.g., the shaft torque peak-to-peak change) at the currentoperating conditions including the measured clutch slip of block 80;actuator signals such as pedal, brake, etc., as shown in block 114;strategy mode switches as shown in block 116; the base table of requiredclutch slip versus operating conditions of block 98; and the NVH levelversus the magnitude of the sensed parameter (e.g., the torquepeak-to-peak change) of block 100. Controller 32 commands the transientclutch slip request to clutch valve 26 in order to control the clutchslip accordingly as shown in block 118.

Controller 32 employs the following operations in identifying thetransient clutch slip request. Controller 32 predicts future operatingconditions based on current operating conditions and changes in theactuator inputs. Controller 32 identifies the magnitude of the sensedparameter (e.g., the shaft torque peak-to-peak change) at the predictedoperating state using the updated table of the torque peak-to-peakchange versus operating conditions of block 82. Controller 32 uses theabove-described operations employed in calculating the static clutchslip request in the context of the transient clutch slip to calculatethe transient clutch slip request. Controller 32 combines the static anddynamic (transient) clutch slip requests (for example, by utilizing aPID controller with feed forward term to obtain the overall clutch sliprequest.

Referring now to FIG. 5A, with continual reference to FIGS. 4 and 5, aflowchart 130 describing operation of the control strategy inarbitrating between static slip request 102 and transient slip request118 is shown. A decision is made in block 132 as to which one of staticslip request 102 and transient slip request 118 to use. The decision isbiased towards selecting the smaller slip request. The selected sliprequest is output for use as shown in block 134.

Referring now to FIG. 6, a flowchart 120 describing operation of thecontrol strategy in an off-line identification process for building basetables is shown. Again, the magnitude of the transmission input shafttorque peak-to-peak change will be used as the representative example.The off-line identification process includes determining therelationship of NVH rating versus the magnitude of the sensed parameter(e.g., shaft torque peak-to-peak change) and operating conditions asshown in block 122. The tables are built using this relationshipinformation as shown in block 124. From these tables, the allowedmagnitude of the sensed parameter (e.g., the allowed shaft torquepeak-to-peak change) based on a current operation condition can beidentified as shown in block 126. Likewise, from these tables, theallowed clutch slip based on the current operating condition and themagnitude of the sensed parameter (e.g., the shaft torque peak-to-peakchange) can be identified as shown in block 128. The allowed clutch slipis further adapted during vehicle operation as shown in block 128.

The following operations are employed in the off-line identificationprocess for building base tables. A structured vehicle NVH drive isperformed to evaluate vehicle NVH level versus the magnitude of thesensed parameter (e.g., the shaft torque peak-to-peak change) forvarying vehicle operating conditions. Look-up tables for the magnitudeof the sensed parameter (e.g., the shaft torque peak-to-peak change)versus allowed NVH level are constructed. Base tables for clutch slipversus the magnitude of the sensed parameter (e.g., the shaft torquepeak-to-peak change) to achieve the allowed NVH level are alsoconstructed.

While exemplary embodiments are described above, it is not intended thatthese embodiments describe all possible forms of the present invention.Rather, the words used in the specification are words of descriptionrather than limitation, and it is understood that various changes may bemade without departing from the spirit and scope of the presentinvention. Additionally, the features of various implementingembodiments may be combined to form further embodiments of the presentinvention.

What is claimed is:
 1. A method for a powertrain having a transmissionand a clutch, comprising: adjusting slip of the clutch to a predefinedtarget in which torque of a shaft of the transmission corresponds to aspecified level of noise, vibration, and harshness (NVH) in thepowertrain.
 2. The method of claim 1 wherein: the shaft is an inputshaft of the transmission.
 3. The method of claim 1 wherein: the shaftis an output shaft of the transmission.
 4. The method of claim 1 furthercomprising: sensing the torque of the shaft using a sensor incommunication with the shaft; and detecting an amount of NVH in thepowertrain based on the torque of the shaft.
 5. The method of claim 4wherein: adjusting includes adjusting the slip of the clutch to thetarget such that the amount of NVH in the powertrain based on the torqueof the shaft corresponds to the specified level of NVH.
 6. The method ofclaim 4 wherein: detecting includes detecting the amount of NVH based ona magnitude of the torque of the shaft, wherein the magnitude of thetorque is one of peak-to-peak change, half peak-to-peak change, androot-mean-square of the torque of the shaft.
 7. The method of claim 1further comprising: obtaining the target of the slip of the clutch froma database having corresponding clutch slip target and specified levelof NVH pairs.
 8. A method for a powertrain having a transmission and aclutch, the method comprising: detecting an amount of noise, vibration,and harshness (NVH) in the powertrain based on torque of a shaft of thetransmission; and adjusting slip of the clutch to a predefined targetcorresponding to a specified level of NVH upon the amount of NVHexceeding the specified level.
 9. The method of claim 8 furthercomprising: sensing the torque of the shaft using a sensor incommunication with the shaft to detect the amount of NVH based on thetorque of the shaft.
 10. The method of claim 8 wherein: the shaft is aninput shaft of the transmission.
 11. The method of claim 8 wherein: theshaft is an output shaft of the transmission.
 12. The method of claim 8wherein: the amount of NVH is detected based on a magnitude of thetorque of the shaft, wherein the magnitude of the torque is one ofpeak-to-peak change, half peak-to-peak change, and root-mean-square ofthe torque of the shaft.
 13. The method of claim 8 further comprising:obtaining the target of the slip of the clutch from a database havingcorresponding clutch slip target and specified level of NVH pairs.
 14. Amethod for a powertrain having a transmission and a clutch, comprising:adjusting slip of the clutch to a predefined target in which a sensedparameter of an output shaft of the transmission corresponds to aspecified level of noise, vibration, and harshness (NVH) in thepowertrain.
 15. The method of claim 14 wherein: the sensed parameter ofthe output shaft is torque of the output shaft.
 16. The method of claim14 wherein: the sensed parameter of the output shaft is speed of theoutput shaft.
 17. The method of claim 14 wherein: the sensed parameterof the output shaft is acceleration of the output shaft.
 18. The methodof claim 14 further comprising: sensing the parameter using a sensor incommunication with the output shaft; and detecting an amount of NVH inthe powertrain based on the sensed parameter of the output shaft. 19.The method of claim 14 wherein: the amount of NVH is detected based on amagnitude of the sensed parameter of the output shaft, wherein themagnitude of the sensed parameter is one of peak-to-peak change, halfpeak-to-peak change, and root-mean-square of the magnitude of the sensedparameter.
 20. The method of claim 14 further comprising: obtaining thetarget of the slip of the clutch from a database having correspondingclutch slip target and specified level of NVH pairs.